Author Keywords: trimethylaluminium hydrolysate; stereoregular; poly(propylene oxide); fractionation; end-group analysis; cyclic oligomers 相似文献
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板材在弯曲过程中存在的最突出的问题是弯曲回弹难以精确控制.弯曲卸载后产生的回弹,使弯曲件的形状和尺寸与模具工作部分的形状和尺寸不符.弯曲件的最后形状与整个变形过程有关,模具几何参数、材料性能参数等都会对回弹产生很大影响.在板材弯曲成形智能化控制系统中,准确确定实时识别和预测模型的输入、输出参数是弯曲智能化控制的成功与否以及回弹控制精度高低的关键.本文采用Ls-dyna软件,对U形件弯曲影响回弹的因素进行了分析,得出了影响回弹规律的主要因素.为U形件弯曲智能化控制神经网络参数识别及预测模型输入、输出参数的选择提供依据. 相似文献
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V. Devadoss M. Noel K. Jayaraman C. Ahmed Basha 《Journal of Applied Electrochemistry》2003,33(3-4):319-323
The redox behaviour of Mn3+/Mn2+, Co3+/Co2+ and Ce4+/Ce3+ mediators commonly used in indirect oxidation of organic compounds were evaluated in methane sulfonic acid on a glassy carbon working electrode employing cyclic voltammetry. Manganic methanesulfonate exhibits higher instability in dilute methanesulfonic acid. The solid MnO2 formed during disproportionation on the glassy carbon electrode further affects the reproducibility. Cobaltic methanesulfonate formation occurs only at oxygen evolution region rendering the overall oxidation process less efficient. Ceric methane sulfonate formation is highly efficient over a wide acid concentration range. Ceric methanesulfonate can also be employed over a wide temperature range to oxidize different aromatic compounds. 相似文献
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Partially stereoregular poly(propylene oxide) samples were synthesized via reactions catalysed by a preformed analytically defined trimethylaluminium hydrolysate. These samples were fractionated into two contrastingly different fractions.
1. (i) D-polymers: This fraction constituted the major part (up to 90%). It mainly contained cyclic low molecular weight oligomers (MW < 1000). The linear chains found in D-polymers had hydroxyl end groups. No double bonds could be detected spectroscopically.
2. (ii) K-polymers: This fraction was high molecular weight stereoregular polymer. Stepwise thermal precipitation from dilute isooctane solution of K-polymers yielded a succession of fractions which differed in melting point. It appears that the phase equilibria during the thermal precipitations were not controlled by the molecular weights of species.
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The pitting behaviour of type 321 stainless steel in sulfide-containing chloride aqueous environments was studied using cyclic potentiodynamic polarization. A well-established correlation between H2S and Na2S2O3 in the study of corrosion was applied, that is, H2S was simulated by Na2S2O3. The major factors affecting the pitting corrosion of type 321 stainless steel are the Cl- concentration, solution pH and temperature. The results clearly indicate that both Epit and E
pp decrease with increasing Cl- concentration and temperature, while I
pass is more sensitive to temperature variation. E
pit decreased with decreasing pH in the range 2 < pH < 7.5. The surface morphology and chemistry of the corroded type 321 stainless steel resulting from anodic polarization in 0.01 M S2O
3
2-
-containing Cl- solution were analysed by XRD, SEM and EPMA. A higher concentration of sulfur was found in the pits, and the dark surface film was mainly composed of FeS and -Fe2O3. The results describe the pitting behaviour of type 321 stainless steel in sulfide-containing Cl- aqueous environments. 相似文献
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